Communication systems are known to comprise a plurality of communication units, a limited number of communication resources that are transceived by base stations or repeaters, and a communication resource allocator that allocates the communication units among the plurality of communication units. A communication resource may comprise a time division multiplex (TDM) slot(s), a carrier frequency, a pair of carrier frequencies, or any other means for transceiving RF information.
As is also known, communication systems, or communication sites, may be linked together to form a communication system network. Within a communication system network, a communication unit may operate in any system, or site. When a communication unit is seeking a communication system, or communication site, to monitor, it listens for control channel information to determine if it can ascertain information from it. (Monitoring a communication system or site comprises receiving outbound signalling words (OSW) via the control channel of that particular communication system or site.) If the communication unit is receiving usable information from the control channel, i.e. the signal strength of the received OSWs is acceptable for the communication unit's receiver, the communication unit monitors this communication system or site.
Once a communication unit is monitoring a particular communication system or site, i.e., receiving OSWs on the control channel of that system, the communication unit assumes that it has full access to that particular communication system, i.e. it can transmit and receive audio and data information. Depending on the communication unit's location within the system or site, it may be capable of receiving OSWs, but it may not be able to accurately transmit inbound signalling words (ISW) to the communication resource allocator. This unfortunate situation occurs because of the transmission power differences between a communication unit and a communication resource allocator. A typical communication resource allocator has a transmission power of about 100 Watts, while a communication unit's transmission power varies from a few Watts to 35 Watts. Thus, even though the communication unit is able to receive OSWs, its transmission power is too weak to transmit ISWs accurately.
One technique to overcome this problem is for the communication resource allocator, upon receiving an ISW from the communication unit, to transmit a signal indicating to the communication unit whether it need to raise or lower its transmitting power. This approach improves the transmitting abilities of the communication unit, however, the communication unit can only transmit up to its maximum power. Therefore, a need exists for a method that allows a communication unit to seek a communication system to monitor based on the quality, or integrity, of the transmit communication path and the receive communication path.